1. Field of the Invention
This invention relates in general to engines and in particular to a cluster of intermittent detonation engines driven by a common gear in which the detonation products are used as the thrust producing medium.
2. Description of Related Art
A pulse detonation engine is an apparatus which produces a high pressure exhaust from a series of repetitive detonations within a detonation chamber. A fuel is detonated within the chamber, causing a wave which propagates at supersonic speeds. The speeds could approach or exceed Chapman Jouguet detonation velocities. The wave compresses the fluid within the chamber, increasing its pressure, density, and temperature. As the wave passes out an open rearward end of the detonation chamber, thrust is created. The cycle is then repeated.
At high speeds, such as Mach 2 to about Mach 3.5, such an engine would be theoretically more efficient than conventional turbojets because the engine does not require compressors or turbines. A pulse detonation engine supplying the same amount or more of thrust as a conventional gas turbine engine would theoretically weigh less. Although a pulse detonation engine weighs less than gas turbine engines producing the same amount of thrust, there is always a desire to increase the thrust to weight ratio of any engine.
Pulse detonation engines have the advantage of not having stall problems as do gas turbine engines. Gas turbine engines develop separation in and around the compressor blades when loaded up, which leads to stall and unstart problems. Clusters of gas turbine engines also have the problem where one stalled engine will also create stall in the other engines. On the other hand, pulse detonation engines are totally isolated in terms of inlet interactions from engine to engine.
A pulse detonation cluster according to the present invention eliminates inlet unstart occurrences and increases the thrust to weight ratio of a group of engines. The pulse detonation cluster includes a cluster housing and several pulse detonation engines disposed within the housing. The cluster housing has a common inlet that is shared by the pulse detonation engines.
Each pulse detonation engine includes an outer tubular housing having a cylindrical bore and a plurality of outer housing ports. An inner tubular housing having a cylindrical bore and plurality of inner housing ports is rigidly and concentrically connected within the outer tubular housing. A detonation chamber is formed in the annulus between the inner and outer housings, the detonation chamber having an upstream end wall and an open downstream end.
An outer valve sleeve having a plurality of outer sleeve ports is concentrically and rotatably mounted to an interior of the outer housing, the outer sleeve ports aligning with the outer housing ports when the outer valve sleeve is in an open position and not aligning with the outer housing ports when the outer valve sleeve is in a closed position.
A plurality of fuel delivery members for delivering fuel to the detonation chamber are rigidly disposed in the inner tubular housing, each fuel delivery member aligning with one of the inner housing ports. An inner sleeve having a plurality of inner sleeve ports is concentrically and rotatably carried on an exterior of the inner housing. The inner sleeve rotates about a longitudinal axis of the inner tubular housing and has an open position and a closed position, the inner sleeve ports aligning with the inner housing ports when the inner sleeve is in the open position and blocking the inner housing ports when the inner sleeve is in the closed position.
A plurality of radial spars are rigidly connected between the outer valve sleeve and the inner sleeve. The radial spars insure that both the outer sleeve and the inner sleeve will rotate together at the same angular velocity.
An external drive system is used to rotate a common gear which matingly engages the outer valve sleeve of each pulse detonation engine in the cluster housing. Since the opening and closing of all the outer valve sleeves are controlled by the common gear, the engines can be easily timed and coordinated to share inlet air from the common inlet of the cluster housing. When properly timed, a pulse detonation cluster having four pulse detonation engines will run smoothly and will have very little bypass air.
A bank of engines includes a bank housing and two or more pulse detonation clusters. By combining two clusters within a bank housing having a common inlet, the eight pulse detonation engines (four in each cluster) can be properly timed to consume all of the air entering the inlet of the bank housing.